1. Field of the Invention
The present invention relates in general to a method for adjusting oscillator frequencies. In particular, the present invention relates to a method for adjusting frequencies of voltage-controlled oscillators.
2. Description of the Related Art
FIG. 1A shows layers 11xcx9c14 of a printed circuit board (PCB) of a conventional voltage-controlled oscillator (VCO). The first layer 11 is a conductive layer comprising circuit components, such as inductors, resistors, transistors and capacitors, connected with each other. There is an insulation layer 15 between every two conductive layers. Defective PCBs usually cause frequency fluctuations. A conventional method for adjusting the frequency of VCO is to cut the inductor 111 of the first layer 11 into a comb-like profile using laser beams from the top of the PCB as the diagram shown in FIG. 1B. The cuttings are performed on part numerated 1,2 and 3 to change the inductance and further rectify the frequency. After the rectification of the frequency, a metal lid 16 is applied, as shown in FIG. 1C, and the manufacturing process of the voltage-controlled oscillator is completed.
The manufacturing process described adjusts the frequency before the lid is applied. However, when the metal lid is applied, the amount of tin soldering the cover to the PCB and the metal lid itself will cause a change in the frequency. When the frequency is high, the variation is high, compromising the yield of final products.
An object of the present invention is to provide a method for adjusting the frequency of an oscillator. The method comprises providing a substrate having a plurality of openings, forming a first conductive layer on a first surface of the substrate and patterning the first conductive layer to form a plurality of strip lines, wherein one strip line is formed corresponding to the location of the openings to become an inductance circuit, covering the conductive layer with a lid, and cutting part of the strip line through the plurality of openings from the opposite side of the first surface to adjust frequencies of the oscillator.
According to the present invention, the one strip line has a plurality of hollow sections of any shape.
According to the present invention, the cutting process uses a laser beam to cut the strip line through the plurality of openings of the substrate to adjust the frequency of the electronic device. The cutting process comprises cutting the space between the plurality of hollow sections and the edge of the strip line. The space between the plurality of hollow sections and the edge of the strip line is adjustable. The cuttings are perpendicular to the edge of the strip line. The method of the present invention further comprises forming a plurality of another conductive layers between the first conductive layer described and the lid. An insulation layer is formed between the conductive layers, and between the substrate and the conductive layer. The insulation layers are fiberglass or epoxy resin glass and have a plurality of through holes filled with a conductive material to couple the circuit components of the plurality of conductive layers.